Brian Kennish is a former Google engineer who never intended to found a startup, much less one that helps people protect their online privacy. He had been making his living writing apps that use people's online activities.

About 18 months ago, Kennish had been happily writing advertising apps for Google. But he discovered something that shook him.

"I had been on other side, doing data tracking at Google, and at DoubleClick before that. I helped write some of the original ad servers. I was knee deep," he recounts. "But the thing that alarmed me was that even I had no idea how many third-party places my data was going to online."

In researching a talk on online tracking for a conference called Defcon, he was shocked to learn that in addition to 1,000 top level sites collecting data on users, another 7,000 third parties were tracking users' activities. (Here's a YouTube of his talk.)

And this stuff was starting to be attached to people's real names, too, thanks to Facebook. When the news broke last year that Facebook had been accidentally leaking people's personal data to its application developers, Kennish took action. (Facebook has since plugged that hole).

"I spent three or four hours writing a Chrome browser extension and called it Facebook Disconnect. I uploaded it to the Chrome store and didn't think anything more about it. I had done extensions before. But this one got media attention. Within a few weeks 50,000 people had installed the thing."

That might have been that, but something else was bugging him. He came to work at Google because he loved the culture of always putting users first. Google had beat out other search engines for doing things like not sneaking paid search results in with organic results.

But that was changing.

A couple of weeks after writing Facebook Disconnect, he made the "hard decision to leave," he says. "I felt like the user wasn't being put first anymore. Compromises were being made today that Google in 2003 wouldn't have made. What I would have called ambition turned into something more like greed."

Disconnect.me was launched in 2010 along with co-founders Austin Chau, fellow Google engineer, and privacy advocate Casey Oppenheim. The company has since raised about $600,000 in seed funding from Highland Capital Partners, and Charles River Ventures, Kennish says.

It has since been extended to block tracking from Google, Twitter, LinkedIn. It's still free as a browser extension in Chrome, Firefox and Safari. Internet Explorer is coming soon. Over 400,000 people are using Disconnect.me and when the company hits a million users, it hopes to launch a paid service.

Eventually, Kennish sees a market to be made in not just letting people control their data, but in selling it. This could work something like how people can put ads on their personal blogs today.

The funny thing is, Kennish isn't even one of those privacy alarmists. "I don't care that much about my own privacy," he says. "I care a little bit about this stuff. If you give me a simple tool to protect my privacy and doesn't interfere with how I use web, I'm going to do that."